The present invention relates to a protective device for a clean robot, which is capable of immediately stopping the robot without a speed reducer of the robot being damaged due to overload in a case where a part of the robot or an object being conveyed by the robot interferes with a surrounding substance.
Conventionally, a clean robot has been known, which is used as a conveyor apparatus of wafer and liquid crystal substrates in the processes of production and inspection of semiconductors and liquid crystal display panels. Such a clean robot is composed as shown in FIG. 9.
In the drawing, 1 denotes a clean robot in charge of handling work in clean surroundings, 2 denotes a fork that receives and transfers an objected to be transferred such as wafer, etc., 3 denotes a robot arm that is rotatable around the rotating axis secured in the clean robot 1, 3A denotes the first robot arm having the fork 2 attached at the tip end thereof, 3B denotes the second robot arm attached to the base end part of the first robot arm 3A, 4 and 5 denote actuators that drive the robot arms 3, 4A denotes the first drive motor, 4B denotes the first speed reducer coupled to the first drive motor 4A, 5A denotes the second drive motor, and 5B denotes the second speed reducer coupled to the second drive motor 5A. 6 denotes a drive drum that rotates the robot arms 3 via the actuators 4 and 5, and 7 denotes a base in which the actuators 4 and 5, and the drive drum 6 are accommodated. 8 denotes a translational guide that causes the base 7 to travel in the rectilinear direction, 9 denotes an actuator of the translational guide 8, and 10 denotes a robot controller that issues instructions to drive and control the actuators 4, 5 and 9.
In the clean robot 1 thus constructed, drive instructions are given from the robot controller 10 to the actuators 4, 5 and 9, wherein the robot arms 3 are caused to turn, extend and contract, and at the same time a wafer is transferred and received by the fork 2 attached to the tip end of the first robot arm 3A by combinations of travelling motions by the translational guide 8.
However, in prior arts, there are cases where an operator makes a mistake in the teaching operations of the robot, and the fork, robot arms of the clean robot, and/or an object to be transferred such as wafer, etc., interfere with substances such as a semiconductor production device, inspection device, etc., which are installed in the surroundings thereof. At this time, since the drive motor that drives the robot arms attempts to further actuate the robot arms even if the clean robot interferes with the surrounding substances, the speed reducer, which is provided between the drive motor and the robot arms, is overloaded, and in the worst case, the speed reducer may be damaged.
It is therefore an object of the invention to provide a protective device for a clean robot that is capable of safely stopping the operations of the clean robot when a part of the clean robot or an object to be transferred by the robot interferes any surrounding substance, and preventing in advance the speed reducer from being damaged.
The present invention provides a clean robot that comprises robot arms that are capable of holding a fork for receiving and transferring a substance such as wafer at the tip ends thereof, and turning, extending and contracting in the horizontal direction; a base that is disposed at the lower part of the abovementioned robot arm and internally accommodates an actuator consisting of a drive motor for driving the abovementioned robot arm and a speed reducer coupled to the abovementioned drive motor; a translational guide provided so that it can rectilinearly move the abovementioned base in the horizontal direction; and a robot controller for driving and controlling the abovementioned robot arms and translational guide; and further includes a signal processing circuit that comprises acceleration sensors that are disposed inside the abovementioned base and provided in respective axes so that they can detect an impact, which is given by interference of the abovementioned clean robot with any surrounding substance, as a vibration acceleration in three-axis directions orthogonal to each other; interference detection means that are provided in contact with the acceleration sensors of the respective axes and outputs a pulse signal when the detection signal of the abovementioned acceleration sensors exceeds a certain threshold value; a first AND circuit for converting the signals, which are outputted from the interference detection means of the respective axes, to interference signals; wherein after the interference signals outputted from the abovementioned signal processing circuit are transmitted to the abovementioned robot controller, the drive motor of the abovementioned actuator is stopped.
Also, the abovementioned interference detection means is composed of a buffer amplifier converting acceleration signals from the abovementioned acceleration sensor with respect to impedance; a band-pass filter for discriminating the frequency band of output signals of the vibration acceleration that is impedance-converted by the buffer amplifier; an amplifier for amplifying the output signals of the abovementioned band-pass filter; the first and second-comparators for comparing the output signals of the vibration acceleration, which are amplified by the abovementioned amplifier, with the upper limit signal and lower limit signal of the vibration acceleration, which become the abovementioned threshold values; and the second AND circuit for converting the signals compared by the abovementioned two comparators to signals, which output interference when the signals exceed any one of the threshold values.
Further, the invention is featured in that a latch circuit, which holds a pulse signal from the abovementioned interference detection means for longer than the sampling time of the abovementioned robot controller, between the abovementioned first AND circuit and the abovementioned robot controller, and all the interference detecting signals can be detected by the abovementioned robot controller.
By the abovementioned means, the acceleration sensor secured in the base of the clean robot can detect, as vibration acceleration in the three-dimensional directions, an impact received when the robot is brought into collision with or interferes with a surrounding substance, and the interference detection means, which is connected to the acceleration sensor of the respective axes, outputs a pulse signal when the detection signal of the sensor exceeds the reference threshold values and the first AND circuit converts the signal, which is outputted from the interference detection means of the respective axes, to an interference signal. Therefore, after the interference-detecting signal is sent to the robot controller, it is possible to immediately stop the drive motors of actuators for the robot arms and translational guide.